A heat resistant, laminated conveyor belt

Abstract: The present invention provides a heat-resistant, laminated conveyer belt (14) comprising an reinforcing layer (11) obtained by impregnating fluoroplastic into a heat-resistant fiber base cloth, drying and sintering the base cloth and a wear-resistant layer (12), formed on the reinforcing layer (11), obtained by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fiber in the form of a knit weave, drying and sintering the base cloth, and its manufacturing method.

Description: The present invention relates to a heat-resistant, laminated conveyer belt and more particularly to a heat-resistant, laminated conveyer belt used in conveying all flat materials such as cardboard, resin made tile, and to its manufacturing method. In the past, as a conveyer belt used in conveying flat materials, e.g., paper and cardboard, there has been known a conveyer belt in which two to six belts base materials of the same type are laminated through a PFA fluorocarbon resin film, and the conveyer belt made up of two or more layers of belt base materials has been used according to the strength required for its application. FR-A-2 386 634 describes a process for producing a fabric in which a support or base cloth is covered by fluorohydrocarbons, polyimides or polyester ureates. That base cloth is described to be a fabric, to be braided or knitted, to be a needle-pounched felt or just a regular foil sheet. The structure described in this document is absolutely symmetric. Even though it is described that such a construct can be used as transport belt, it is also described that it suffers from mechanical constraints. Therefore silicates and grains should be included into the materials used in order to overcome these defects. FIG. 4 shows a conventional conveyer belt. This conveyer belt is formed by sandwiching a PFA fluorocarbon resin film 43 between heat-resistant fiber cloths 41 and 42. The heat-resistant fiber cloths are woven cloths made of glass fiber, carbon fiber, aramid fiber and aromatic allylate fiber, and they are also woven in the form of plain weave, satin weave and twill weave. Moreover, the heat-resistant cloth is impregnated on, at least, one side of the surface with TFE fluorocarbon resin, dried, and sintered, and it follows that this composite possesses exceptional properties, that is, high chemical resistance, heat resistance, ant-stick proerty, and wear resistance. Furthermore, in some cases, an one-layer belt is used under high tension. However, normally, the conveyer belt, which is made up of two or more layers, is used. However, when two above-mentioned fluoroplastic composites with the heat-resistant cloths of the sameweave are thermally pressurized, thereby obtaining a two-layer belt, the upper layer (hereinafter called "the wear-resistant layer") cannot follow the expansion and contraction of the lower layer (hereinafter called "the reinforcing layer") because of the difference in the circumferential length between the wear-resistant layer and the reinforcing layer. As a result, a surface separation occurs between the heat-resistant fiber cloths and the impregnated fluoroplastic layer inside the wear-resistant layer by the shearing stress of the surface between the reinforcing layer and the wear-resistant layer and/or the shearing stress of the wear-resistant layer itself. Due to this, there is a problem in that the original properties of fluoroplastic are lost and the lifetime of the belt is shortened. An object of the present invention is to provide a heat-resistant, laminated conveyer belt which has a long lifetime without losing the original fluoroplastic properties by comprising a wear-resistant layer with good flexibility. Moreover, another object of the present invention is to provide a method for manufacturing such a heat-resistant, laminated conveyer belt, which has a long lifetime without losing the original fluoroplastic property. According to the present invention, there is obtained a heat-resistant, laminated conveyer belt comprising a reinforcing layer and a wear-resistant layer, said reinforcing layer being thermally pressure-bonded to said wear-resistant layer, wherein said wear-resistant layer has the ability of expansion and contraction and is obtained by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fibers in form of a knit weave, drying and sintering said base cloth. Said reinforcing layer is obtained by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fibers in a weave form different from the knit weave, drying, and sintering said base cloth. Also, according to the present invention, there is provided a method for manufacturing a heat-resistant, laminated conveyer belt comprising the steps of forming a wear-resistant layer having the ability of expansion and extraction by impregnating fluoroplastic into a heat-resistant fiber base cloth formed by weaving heat-resistant fibers in the form of a knit weave, drying and sintering said base cloth; and forming a reinforcing layer by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fiber in a weave form different from the knit weave, drying and sintering the base cloth and thermally pressure bonding the reinforcing layer to the wear-resistant layer. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: FIG. 1A is a plan view of a heat-resistant, laminated conveyor belt of one embodiment of the present invention; FIG. 1B is a cross sectional view taken along a line of X-X of FIG. 1A; FIG. 2 is a view explaining a knit weave according to the present invention; FIG. 3 is a view explaining a running test of the heat-resistant conveyer belt of FIG. 1A; and FIG. 4 is a view explaining a conventional layer belt. In the present invention, as a heat-resistant fiber cloth, there can be used glass fiber, carbon fiber, aramid fiber, aromatic allylate fiber. Particularly, glass fiber or aramid fiber is desirably used. As fluoroplastic, there can be used polytetrafluoroethylene (PTFE), polytetrafluoroethylene-perfluoroalky vinyl ether copolymer (PFA), tetrafluoroethylene hexafluoropropylene copolymer (FEP) in a single form or a form of mixture of two or more kinds, Also, heat-resistant filler may be mixed into fluoroplastic in order to much improve wear resistance of the wear-resistant layer. As the weaving method of the woven cloth, there are a plain weave, a satin weave, twill weave, and a knit weave. When the composite materials, which are obtained by impregnating fluoroplastic into the woven cloth of the same weaving method, drying and sintering the woven cloth, are laminated in a two-layer belt shape through a PFA film by thermal pressurization, a surface separation occurs particularly between the heat-resistant fiber cloths and fluoroplastic layer of the wears resistant layer because of the shearing stress caused by a difference in a circumferential length between the rein-forcing layer and the wear-resistant layer. Therefore, according to the present invention, in the two-layer belt shape, the combinations of the reinforcing layer cloth and the wear-resistant layer cloth such as the plain wave - knit weave, the satin weave - knit weave, and the twill weave - knits weave, are preferable. FIG. 2 is a view explaining the knit weave using a knit weaving material 21. In an alternative embodiment of the present invention, a non-woven fabrious mat, which is made up of heat-resistant, corrugated short fiber or heat-resistant spring-shaped short fiber itself, could also be used as the base material of the wear-resistant layer. In that case, the wear-resistant layer is formed in the following steps: the above mentioned mat is impregnated with fluoroplastic then dried and sintered. In the present invention, the content of fluoroplastic in the reinforcing layer is 80 weight% or less, preferably 30 to 60 weight%. If the content of fluoroplastic exceeds 80 weight%, there is possibility that the flexibility of the conveyer will be lost. If the content of fluoroplastic is below 30 weight%, there is possibility that bowed filling will occur in the woven cloth. On the other hand, the content of fluoroplastic in the wear-resistant layer is 80 weight% or less, preferably 30 to 60 weight%. If the content of fluoroplastic exceeds 80 weight%, the wear-resistant layer cannot follow the expansion and contraction of the reinforcing layer which the present invention intends. As a result, the ability of expansion and contraction and flexibility will be lost. If the content of fluoroplastic is below 30 weight%, there is possibility that wear of the knit weave itself will be promoted and that the maintenance of the shape of the knit weave itself will be lost. According to the present invention, the heat-resistant fiber of the wear-resistant layer is formed into a knit weave or a corrugated or spring-shaped non-woven cloth, thereby providing the ability of expansion and contraction for wear-resistant layer. Therefore, flexibility of the wear-resistant layer can be extremely improved as compared with the conventional layer belt, which is manufactured by the same weave structure, so that the lifetime of the belt can be improved. An embodiment of the present invention will be explained with reference to FIGS. 1A and 1B. FIG. 1A is a plan view of a heat-resistant, laminated conveyer belt, and FIG. 1B is a cross sectional view taken along a line of X-X of FIG. 1A. A reinforcing layer 11 having a thickness of 0.5 mm is formed by impregnating PTFE fluorocarbon resin into a heat-resistant fiber base cloth, and drying and sintering the base cloth. More specifically, the reinforcing layer 11 can be obtained by the following process. A woven cloth is formed by weaving aromatic aramid fiber (trade name: Technora manufactured by Teijin Co., Ltd.) in the form of the plain weave. PEFE fluorocarbon resin dispersion (trade name: Teflon T-30J, manufactured by Mitsui-Du Pont Fluoro Chemical Co., Ltd) is impregnated into the woven cloth. Then, the woven cloth is dried, and sintered at 380°C. This process is repeated several times, thereby the reinforcing layer 11 can be obtained. The wear-resistant layer 12 having a thickness of 0.5 mm is formed on the reinforcing layer 11 through a PFA film 13 having a thickness of 25µm. More specifically, the wear-resistant layer 12 can be obtained by the following process. A woven cloth is formed by weaving aramid fiber (trade name: Technora manufactured by Teijin Co., Ltd.) in the form of the knit weave. PEFE fluorocarbon resin dispersion (trade name; Teflon T-30J, manufactured by Mitsui-Du Pont Fluoro Chemical Co., Ltd) is impregnated into the woven cloth. Then, the woven cloth is dried, and sintered at 380°C. This process is repeated several times, thereby the wear-resistant layer 12 can be obtained. The PFA fluorocarbon resin film 13 is sandwiched between the reinforcing layer 11 as a lower layer and the wear-resistant layer 12 as an upper layer. Then, these laminated layers are thermally pressurized at 380°C under pressure of 0.98 MPa. Then, both ends of the obtained belt-shaped material are butt jointed to each other to be endless. As mentioned above, a heat-resistant, laminated conveyer belt 14 comprises the reinforcing layer 11, which is obtained by impregnating PTFFE fluorocarbon resin into the aromatic aramid fiber base cloth, drying and sintering the base cloth, and the wear-resistant layer 12, which is formed on the reinforcing layer 11 through the PFA fluorocarbon resin film 13 and which is obtained by impregnating PTFFE into the base cloth, which is formed by weaving aramid fiber in the form of the knit weave, drying and sintering the base cloth to provide the ability of expansion and contraction. Therefore, flexibility of the obtained conveyer belt 14 can be extremely improved as compared with the conventional laminated belt, which is manufactured by the same weave structure, so that the lifetime of the belt can be improved. Actually, the running test of the conveyer belt 14 of the above-mentioned embodiment was performed in accordance with the following conditions so as to examine the flexibility. The conveyer belt 14 was set as shown in FIG. 3 by use of drive rolls 31 and 32, pulleys 33, 34, and a load pressure roll 35. Then, the conveyer belt 14 was run under conditions of ambient temperature of 180°C, load of 1.5 kN/cm width and belt running speed of 800 m/minutes. As a result of the running test, the number of times at which the conveyer belt was brokendown was 49,856. On the other hand, regarding the layer belt having the same structure as the above embodiment except the point that the woven cloth of the wear-resistant layer was formed in the form of the plain weave, the above-mentioned number of times was examined. As a result, the number of times was 465. Therefore, it is clear that the present invention is superior to the conventional belt conveyer. As mentioned above, according to the present invention, there is obtained a belt heat-resistant, laminated conveyer which can has the long lifetime without losing the original fluoroplastic properties on the ground that the wear-resistant layer has the excellent ability of expansion and contraction, that is, the excellent flexibility.

Claims: A heat-resistant, laminated conveyer belt comprising a reinforcing layer (11) and a wear-resistant layer (12), said reinforcing layer (11) being thermally pressure-bonded to said wear-resistant layer (12), characterized in that said wear-resistant layer (12) has the ability of expansion and contraction and is obtained by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fibers in form of a knit weave, or into a base cloth consisting of a non-woven cloth formed of shorter fibers having a corrugated shape and a spring-like ability of expansion and contraction, drying and sintering said base cloth; said reinforcing layer (11) is obtained by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fibers in a weave form different from the knit weave, drying, and sintering said base cloth. A conveyor belt according to claim 1, characterized in that said heat-resistant fiber is formed of glass fiber, carbon fiber, aramid fiber, and/or aromatic allylate fiber. A conveyer belt according to any one of the preceding claims, characterized in that the content of fluoroplastic of said reinforcing layer (11) and/or of said wear-resistant layer (12) to the total weight of the layers is 80% or less. A conveyer belt according to any one of the preceding claims, characterized in that the weave form different from the knit weave is any one of a plain weave, a satin weave, and a twill weave. A method for manufacturing a heat-resistant, laminated conveyer belt comprising the steps of: forming a wear-resistant layer (12) having the ability of expansion and contraction by impregnating fluoroplastic into a heat-resistant fiber base cloth formed by weaving heat-resistant fibers in the form of a knit weave or consisting of a non-woven cloth formed of shorter fibers having a corrugated shape and a spring-like ability of expansion and contraction, drying and sintering said base cloth; and forming a reinforcing layer (11) by impregnating fluoroplastic into a base cloth formed by weaving heat-resistant fiber in a weave form different from the knit weave, drying and sintering the base cloth and thermally pressure bonding the reinforcing layer (11) to the wear-resistant layer (12). A method according to claim 5, characterized in that said heat-resistant fiber is formed of glass fiber, carbon fiber, aramid fiber, and/or aromatic allylate fiber. A method according to any one of claims 5 or 6, characterized in that the content of fluoroplastic of said reinforcing layer (11) and/or of said wear-resistant layer (12) to the total weight of the layers is 80% or less. A method according to any one of claims 5 to 7, characterized in that as weave form different from the knit weave any one of a plain weave, a satin weave, and a twill weave is used.

Inventors: HARAGUCHI TOMOMI, ISHIBASHI MASANORI, KITAGAWA SUMIO, NOGAMI YOSHIRO, HARAGUCHI, TOMOMI, ISHIBASHI, MASANORI, KITAGAWA, SUMIO, NOGAMI, YOSHIRO
Applicants: CHUKOH CHEM IND, CHUKOH CHEMICAL INDUSTRIES LTD.
Application year: 1994
Main classification: B65G15
IPC codes: D06M17, B32B5, D06M15, D06N7, D06N3, B65G15